Summary of Work: Study Objective: To examine the relationships among severity of illness, quality of life, and functional ability and to determine the impact of oxygen therapy on functional ability in patients with alpha-1 antitrypsin deficiency. Methods: Patients responded to a questionnaire that measures four aspects of quality of life: emotional function, fatigue, mastery, and dyspnea. Patients walk for 6 minutes with oxygen via nasal cannula or with placebo. Measurements include the distance walked, the oxygen saturation and pulse rate during the walk, and the dyspnea intensity at the end of each walk. Summary of Findings: To date we have collected data on 33 subjects. Data analysis indicates no advantage of oxygen over placebo in terms of the outcome measures. Accrual of subjects for this portion of the study has stopped. An amendment to this protocol was approved to test patients with more advanced disease, comparing oxygen with paced breathing. Subjects enrolled in the oxygen group (n = 12) were able to walk farther and had a higher oxygen saturation compared with the paced breathing group (N = 8). However, dyspnea was not different between the two groups. The unusual walking rhythm during paced breathing was uncomfortable for some subjects. An amendment has been approved to evaluate quality of life in patients with alpha-1 antitrypsin deficiency who have normal lung function. Data collection for this amendment continues.